[PATCH V6 06/14] powerpc/vas: Setup thread IRQ handler per VAS instance
Haren Myneni
haren at linux.ibm.com
Thu Mar 5 07:47:41 AEDT 2020
Setup thread IRQ handler per each VAS instance. When NX sees a fault
on CRB, kernel gets an interrupt and vas_fault_handler will be
executed to process fault CRBs. Read all valid CRBs from fault FIFO,
determine the corresponding send window from CRB and process fault
requests.
Signed-off-by: Sukadev Bhattiprolu <sukadev at linux.vnet.ibm.com>
Signed-off-by: Haren Myneni <haren at linux.ibm.com>
---
arch/powerpc/platforms/powernv/vas-fault.c | 90 +++++++++++++++++++++++++++++
arch/powerpc/platforms/powernv/vas-window.c | 60 +++++++++++++++++++
arch/powerpc/platforms/powernv/vas.c | 49 +++++++++++++++-
arch/powerpc/platforms/powernv/vas.h | 6 ++
4 files changed, 204 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/platforms/powernv/vas-fault.c b/arch/powerpc/platforms/powernv/vas-fault.c
index 4044998..85e4280 100644
--- a/arch/powerpc/platforms/powernv/vas-fault.c
+++ b/arch/powerpc/platforms/powernv/vas-fault.c
@@ -11,6 +11,7 @@
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/kthread.h>
+#include <linux/mmu_context.h>
#include <asm/icswx.h>
#include "vas.h"
@@ -25,6 +26,95 @@
#define VAS_FAULT_WIN_FIFO_SIZE (4 << 20)
/*
+ * Process valid CRBs in fault FIFO.
+ */
+irqreturn_t vas_fault_thread_fn(int irq, void *data)
+{
+ struct vas_instance *vinst = data;
+ struct coprocessor_request_block *crb, *entry;
+ struct coprocessor_request_block buf;
+ struct vas_window *window;
+ unsigned long flags;
+ void *fifo;
+
+ crb = &buf;
+
+ /*
+ * VAS can interrupt with multiple page faults. So process all
+ * valid CRBs within fault FIFO until reaches invalid CRB.
+ * NX updates nx_fault_stamp in CRB and pastes in fault FIFO.
+ * kernel retrives send window from parition send window ID
+ * (pswid) in nx_fault_stamp. So pswid should be valid and
+ * ccw[0] (in be) should be zero since this bit is reserved.
+ * If user space touches this bit, NX returns with "CRB format
+ * error".
+ *
+ * After reading CRB entry, invalidate it with pswid (set
+ * 0xffffffff) and ccw[0] (set to 1).
+ *
+ * In case kernel receives another interrupt with different page
+ * fault, CRBs are already processed by the previous handling. So
+ * will be returned from this function when it sees invalid CRB.
+ */
+ do {
+ mutex_lock(&vinst->mutex);
+
+ spin_lock_irqsave(&vinst->fault_lock, flags);
+ /*
+ * Advance the fault fifo pointer to next CRB.
+ * Use CRB_SIZE rather than sizeof(*crb) since the latter is
+ * aligned to CRB_ALIGN (256) but the CRB written to by VAS is
+ * only CRB_SIZE in len.
+ */
+ fifo = vinst->fault_fifo + (vinst->fault_crbs * CRB_SIZE);
+ entry = fifo;
+
+ if ((entry->stamp.nx.pswid == FIFO_INVALID_ENTRY) ||
+ (entry->ccw & CCW0_INVALID)) {
+ atomic_set(&vinst->faults_in_progress, 0);
+ spin_unlock_irqrestore(&vinst->fault_lock, flags);
+ mutex_unlock(&vinst->mutex);
+ return IRQ_HANDLED;
+ }
+
+ spin_unlock_irqrestore(&vinst->fault_lock, flags);
+ vinst->fault_crbs++;
+ if (vinst->fault_crbs == (vinst->fault_fifo_size / CRB_SIZE))
+ vinst->fault_crbs = 0;
+
+ memcpy(crb, fifo, CRB_SIZE);
+ entry->stamp.nx.pswid = FIFO_INVALID_ENTRY;
+ entry->ccw |= CCW0_INVALID;
+ mutex_unlock(&vinst->mutex);
+
+ pr_devel("VAS[%d] fault_fifo %p, fifo %p, fault_crbs %d\n",
+ vinst->vas_id, vinst->fault_fifo, fifo,
+ vinst->fault_crbs);
+
+ window = vas_pswid_to_window(vinst,
+ be32_to_cpu(crb->stamp.nx.pswid));
+
+ if (IS_ERR(window)) {
+ /*
+ * We got an interrupt about a specific send
+ * window but we can't find that window and we can't
+ * even clean it up (return credit).
+ * But we should not get here.
+ */
+ pr_err("VAS[%d] fault_fifo %p, fifo %p, pswid 0x%x, fault_crbs %d bad CRB?\n",
+ vinst->vas_id, vinst->fault_fifo, fifo,
+ be32_to_cpu(crb->stamp.nx.pswid),
+ vinst->fault_crbs);
+
+ WARN_ON_ONCE(1);
+ atomic_set(&vinst->faults_in_progress, 0);
+ return IRQ_HANDLED;
+ }
+
+ } while (true);
+}
+
+/*
* Fault window is opened per VAS instance. NX pastes fault CRB in fault
* FIFO upon page faults.
*/
diff --git a/arch/powerpc/platforms/powernv/vas-window.c b/arch/powerpc/platforms/powernv/vas-window.c
index 1783fa9..7c6f55f 100644
--- a/arch/powerpc/platforms/powernv/vas-window.c
+++ b/arch/powerpc/platforms/powernv/vas-window.c
@@ -1040,6 +1040,15 @@ struct vas_window *vas_tx_win_open(int vasid, enum vas_cop_type cop,
}
} else {
/*
+ * Interrupt hanlder or fault window setup failed. Means
+ * NX can not generate fault for page fault. So not
+ * opening for user space tx window.
+ */
+ if (!vinst->virq) {
+ rc = -ENODEV;
+ goto free_window;
+ }
+ /*
* A user mapping must ensure that context switch issues
* CP_ABORT for this thread.
*/
@@ -1254,3 +1263,54 @@ int vas_win_close(struct vas_window *window)
return 0;
}
EXPORT_SYMBOL_GPL(vas_win_close);
+
+struct vas_window *vas_pswid_to_window(struct vas_instance *vinst,
+ uint32_t pswid)
+{
+ int winid;
+ struct vas_window *window;
+
+ if (!pswid) {
+ pr_devel("%s: called for pswid 0!\n", __func__);
+ return ERR_PTR(-ESRCH);
+ }
+
+ decode_pswid(pswid, NULL, &winid);
+
+ if (winid >= VAS_WINDOWS_PER_CHIP)
+ return ERR_PTR(-ESRCH);
+
+ /*
+ * If application closes the window before the hardware
+ * returns the fault CRB, we should wait in vas_win_close()
+ * for the pending requests. so the window must be active
+ * and the process alive.
+ *
+ * If its a kernel process, we should not get any faults and
+ * should not get here.
+ */
+ window = vinst->windows[winid];
+
+ if (!window) {
+ pr_err("PSWID decode: Could not find window for winid %d pswid %d vinst 0x%p\n",
+ winid, pswid, vinst);
+ return NULL;
+ }
+
+ /*
+ * Do some sanity checks on the decoded window. Window should be
+ * NX GZIP user send window. FTW windows should not incur faults
+ * since their CRBs are ignored (not queued on FIFO or processed
+ * by NX).
+ */
+ if (!window->tx_win || !window->user_win || !window->nx_win ||
+ window->cop == VAS_COP_TYPE_FAULT ||
+ window->cop == VAS_COP_TYPE_FTW) {
+ pr_err("PSWID decode: id %d, tx %d, user %d, nx %d, cop %d\n",
+ winid, window->tx_win, window->user_win,
+ window->nx_win, window->cop);
+ WARN_ON(1);
+ }
+
+ return window;
+}
diff --git a/arch/powerpc/platforms/powernv/vas.c b/arch/powerpc/platforms/powernv/vas.c
index 557c8e4..3d9ba58 100644
--- a/arch/powerpc/platforms/powernv/vas.c
+++ b/arch/powerpc/platforms/powernv/vas.c
@@ -14,6 +14,8 @@
#include <linux/of_platform.h>
#include <linux/of_address.h>
#include <linux/of.h>
+#include <linux/irqdomain.h>
+#include <linux/interrupt.h>
#include <asm/prom.h>
#include <asm/xive.h>
@@ -24,9 +26,53 @@
static DEFINE_PER_CPU(int, cpu_vas_id);
+static irqreturn_t vas_fault_handler(int irq, void *dev_id)
+{
+ struct vas_instance *vinst = dev_id;
+ irqreturn_t ret = IRQ_WAKE_THREAD;
+ unsigned long flags;
+
+ /*
+ * NX can generate an interrupt for multiple faults. So the
+ * fault handler thread process all CRBs until finds invalid
+ * entry. In case if NX sees continuous faults, it is possible
+ * that the thread function entered with the first interrupt
+ * can execute and process all valid CRBs.
+ * So wake up thread only if the fault thread is not in progress.
+ */
+ spin_lock_irqsave(&vinst->fault_lock, flags);
+
+ if (atomic_read(&vinst->faults_in_progress))
+ ret = IRQ_HANDLED;
+ else
+ atomic_set(&vinst->faults_in_progress, 1);
+
+ spin_unlock_irqrestore(&vinst->fault_lock, flags);
+
+ return ret;
+}
+
static int vas_irq_fault_window_setup(struct vas_instance *vinst)
{
- return vas_setup_fault_window(vinst);
+ char devname[64];
+ int rc = 0;
+
+ snprintf(devname, sizeof(devname), "vas-%d", vinst->vas_id);
+ rc = request_threaded_irq(vinst->virq, vas_fault_handler,
+ vas_fault_thread_fn, 0, devname, vinst);
+
+ if (rc) {
+ pr_err("VAS[%d]: Request IRQ(%d) failed with %d\n",
+ vinst->vas_id, vinst->virq, rc);
+ goto out;
+ }
+
+ rc = vas_setup_fault_window(vinst);
+ if (rc)
+ free_irq(vinst->virq, vinst);
+
+out:
+ return rc;
}
static int init_vas_instance(struct platform_device *pdev)
@@ -109,6 +155,7 @@ static int init_vas_instance(struct platform_device *pdev)
list_add(&vinst->node, &vas_instances);
mutex_unlock(&vas_mutex);
+ spin_lock_init(&vinst->fault_lock);
/*
* IRQ and fault handling setup is needed only for user space
* send windows.
diff --git a/arch/powerpc/platforms/powernv/vas.h b/arch/powerpc/platforms/powernv/vas.h
index 9785c81..b82d5da 100644
--- a/arch/powerpc/platforms/powernv/vas.h
+++ b/arch/powerpc/platforms/powernv/vas.h
@@ -326,7 +326,10 @@ struct vas_instance {
u64 irq_port;
int virq;
+ int fault_crbs;
int fault_fifo_size;
+ atomic_t faults_in_progress;
+ spinlock_t fault_lock;
void *fault_fifo;
struct vas_window *fault_win; /* Fault window */
@@ -424,6 +427,9 @@ struct vas_winctx {
extern void vas_window_init_dbgdir(struct vas_window *win);
extern void vas_window_free_dbgdir(struct vas_window *win);
extern int vas_setup_fault_window(struct vas_instance *vinst);
+extern irqreturn_t vas_fault_thread_fn(int irq, void *data);
+extern struct vas_window *vas_pswid_to_window(struct vas_instance *vinst,
+ uint32_t pswid);
static inline void vas_log_write(struct vas_window *win, char *name,
void *regptr, u64 val)
--
1.8.3.1
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